We are currently investigating an issue for Quantrix users that are on the new OS X Sierra 10.12.
It appears that upon window close a Sun / Java error is occurring and an error dialog appears.
While significant, it does not appear to be causing issues are model saving or file corruption but we continue to investigate with high priority. It is more difficult to track down because the error is not occurring in Quantrix code but is reacting adversely to a procedure in Quantrix. So we will continue to investigate with high priority and advise. However, I would recommend that Quantrix users do no upgrade to OS X Sierra until we have fully identified the issue.